leetcode: solve 'int to roman' problem in elixir

leetcode/0012-integer-to-roman/elixir/.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

leetcode/0012-integer-to-roman/elixir/.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+integer_to_roman-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

leetcode/0012-integer-to-roman/elixir/lib/integer_to_roman.ex

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+defmodule Solution do
+  @spec int_to_roman(num :: integer) :: String.t()
+  def int_to_roman(num) do
+    thousands = div(num, 1000)
+    hundreds = div(rem(num, 1000), 100)
+    tens = div(rem(num, 100), 10)
+
+    String.duplicate("M", thousands) <>
+      to_roman(hundreds, "C", "D", "M") <>
+      to_roman(tens, "X", "L", "C") <>
+      to_roman(rem(num, 10), "I", "V", "X")
+  end
+
+  @spec to_roman(num :: integer, one :: String.t(), five :: String.t(), ten :: String.t()) ::
+          String.t()
+  defp to_roman(num, one, five, ten) do
+    case num do
+      x when x <= 3 -> String.duplicate(one, x)
+      x when x == 4 -> one <> five
+      x when x > 4 and x <= 8 -> five <> String.duplicate(one, x - 5)
+      x when x > 8 -> one <> ten
+    end
+  end
+end

leetcode/0012-integer-to-roman/elixir/mix.exs

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+defmodule IntegerToRoman.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :integer_to_roman,
+      version: "0.1.0",
+      elixir: "~> 1.16",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

leetcode/0012-integer-to-roman/elixir/test/integer_to_roman_test.exs

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+defmodule IntegerToRomanTest do
+  use ExUnit.Case
+  doctest Solution
+
+  test "example 1" do
+    assert Solution.int_to_roman(3749) == "MMMDCCXLIX"
+  end
+
+  test "example 2" do
+    assert Solution.int_to_roman(58) == "LVIII"
+  end
+
+  test "example 3" do
+    assert Solution.int_to_roman(1994) == "MCMXCIV"
+  end
+
+  test "smallest number" do
+    assert Solution.int_to_roman(1) == "I"
+  end
+
+  test "largest number" do
+    assert Solution.int_to_roman(3999) == "MMMCMXCIX"
+  end
+end

leetcode/0012-integer-to-roman/elixir/test/test_helper.exs

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+ExUnit.start()

leetcode/0012-integer-to-roman/readme.md

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+# 12. Integer to Roman
+
+[Leetcode](https://leetcode.com/problems/integer-to-roman/)
+
+Given an integer, convert it to a Roman numeral.